1. Field of the Invention
The subject-matter of the invention refers to a sealing arrangement for sealing a reciprocating piston rod of a reciprocating compressor having a first and second sealing elements, and wherein the sealing elements are arranged inside a recess of the sealing arrangement at an axial distance, and wherein the sealing elements are arranged respectively at an axial end of the recess and in contact with the piston rod, and wherein a feed line of a sealing medium is provided in the sealing arrangement that is connected with the recess.
2. The Prior Art
Conventional seals between a reciprocating piston rod, for example of a reciprocating compressor, and a stationary machine component for sealing a space that is under high pressure, for example the operating pressure inside the cylinder of the compressor, relative to a space under low pressure, for example atmospheric pressure in the crankcase of the compressor, are typically implemented as sealing packs. A sealing pack of this type comprises several packing rings and/or packing ring combinations that are axially arranged one after the other. Combinations of a radially cut and a tangentially cut packing ring are used most frequently, as set forth, for example, in EP 1 146 264 A2. Also used, in addition, are segmented ring designs in which a packing ring is composed of several ring segments, as known in the art, for example, from U.S. Pat. No. 4,350,349 A. But seals of this type are not completely (100%) leak-proof systems; they always have a certain amount of leakage escaping through the seal.
In certain applications involving compressors, for example compressor stations for the conveyance of natural gas, it is becoming increasingly important to minimize working medium leakages (for example, natural gas) for environmental reasons (not least of all because the requirements mandated by the legislatures are increasingly being tightened). Therefore, conventional sealing packs would have to meet high requirements; a proposition, however, that is, on the one hand, not always possible to implement and would, on the other hand, at least translate into a considerable increase of complexity in terms of providing sealing action.
The prior art describes seals for two components that are moved relative to each other, for example between a piston rod and a machine housing, operating according to the principle of a “fluid barrier.” In this instance, a sealing medium (for example, oil and another suitable fluid) is supplied between two sealing elements under a higher pressure than ambient pressure, for example the operating pressure inside the cylinder of a compressor. This way, a working medium, for example a gas or air, having a lower pressure level than the pressure of the sealing medium cannot escape through the seal to the outside. An example for such a seal is disclosed, for example, in DE 28 39 243 A1 with oil as a sealing medium or in DE 10 2005 034 908 A1 with an ionic fluid as a sealing medium. Seals of this type are therefore also referred to as gas-proof seals and can be kept leak-proof even during a standstill as long as the pressure of the sealing medium is maintained. However, in these cases there usually occurs leaking of sealing medium, which must be captured correspondingly.
But reciprocating compressors, in particular, are able to execute significant transverse movements, aside from the stroke in axial direction by the piston rod. A seal of a piston rod on a reciprocating compressor must therefore be operable and provide secure sealing action even for such transverse movements.